The cake may be a lie, but rumors that Still Alive will be arriving in Rock Band (Xbox 360, PS3, PS2,) as a downloadable content certainly isn't.

A recent Valve Corporation party over at the Temple night club (just beside the GDC's Moscone theater) has revealed that GLaDOS' finale for the Portal title will indeed be arriving to Harmonix's game.

This news was unveiled by song composer Jonathan Coulton, who was also at the Valve bash.

Harmonix's Dan Teasdale (senior designer) and Alex Rigopulos (company founder) jumped onstage alongside Coulton, who performed this piece on a copy of Rock Band to wrap up the night's festivities.

And from the way hmxsean over at the game'sofficial site describes the experience, it was intense:

The crowd went nuts. Earlier we had turned the backing vocals all the way down and the microphone vocals all the way up so we could actually hear his voice instead of GLaDOS.

Alex was on drums ruling it, and Dan Teasdale held his own on guitar. By the end of the song even the people in the back of the room were screaming.